CAMARILLO, Calif. (AP) — The average price of regular-grade gasoline in the U.S. has remained relatively steady for the past three weeks with a national average of $3.01 per gallon.

Industry analyst Trilby Lundberg of the Lundberg Survey said Sunday that a drop in crude prices has not been seen at the pump. Lundberg says that station operators kept the difference between wholesale and retail prices to make up for tight margins.

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The average on May 18 was a fraction under $3 a gallon.

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The highest average price in the contiguous 48 states was $3.81 in the San Francisco Bay Area. The lowest was $2.54 in Baton Rouge, Louisiana.

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The average price for diesel fuel rose 4 cents, to $3.27.